potential energy

  1. peguerosdc

    B How to relate the gravitational potential energy zero to the axes?

    (Throughout all my post, I will refer to “gravitational potential energy” just as “potential energy”) Hi! I have this confusion about when is potential energy positive/negative and how it is related to how we define our axes. I think it is easier to understand my confusion with the following...
  2. L

    Man jumping onto a see-saw to launch bricks vertically

    I drew a diagram for the a) part The person is h meters high So GPE= 100 x 9.8x h GPE= 980h j KE = 980h when the person hits the see saw KE=1/2mv² 980h=0.5 x 5 x v² Now it v²=u²+2as For the brick going up to 10m v = 0 u=? a=-9.8ms-² s=10m u²=2 x 9.8 x 10 u=14m/s We can assume that u=14m/s is...
  3. J

    B Understanding the derivation for Elastic Potential Energy.

    Elastic Potential Energy of a Strained Body (A) Using ## Y = \frac {stress}{strain}## we get ##F = \frac {AY}{L} * x## where ##F## is the restoring force, ##x## is the distance the body is stretched by. Since Work = PE (spring force/ stress is conservative?) Thus ##W = \int_{0}^{x} \frac...
  4. Harperchisari

    I The energy conservation issue with parallel charged plates with a hole.

    A while back I thought of an issue with parallel charged plates. Imagine this: a set of opposite charged resistive plates with holes in the center. In theory, there is a finite amount of energy required to push a positive charged particle through the hole in the positive plate (in theory it...
  5. Gursimran Singh

    Potential energy of a shell and a disc, both covered uniformly with charge

    Double integration maybe?? I calculated potential due to shell on plate's center but not on other points on it's surface.
  6. M

    Force on a pin from a pendulum and a string

    1. Determine the velocity of the ball when it is 30degrees from the horizontal: U1 = mgh = mg(0.8m) U2 = mgh = mg(0.4+0.4cos(30)) = mg(.74641) ΔU = U2 - U1 = mg(.74641 - .8) = mg(-0.051433) T1 =0 T2 = 0.5mv^2 ΔT = T2 - T1 = 0.5mv^2 ΔU = ΔT mg(-0.051433) = 0.5mv^2 ====> v = 1.025394 2. Use...
  7. M

    How far does the block slide? (work, spring, incline)

    1. Homework Statement The system is released from rest with no slack in the cable and with the spring stretched 225 mm. Determine the distance s traveled by the 3.2-kg cart before it comes to rest (a) if m approaches zero and (b) if m = 2.5 kg. Assume no mechanical interference and no friction...
  8. L

    B Potential Energy and Potential -- Systems versus Particles

    When I first learned about these subjects, I did what was intuitive to me and treated particles as if they carried potential energy. I would do this similarly for rigid bodies where I would also treat them as a particles with their body's mass at the center of mass. This wasn't helped by...
  9. S

    I Relativistic mass and gravitational potential

    Hello everyone, Any object has a gravitational potential energy as a function of the distance from the earth (R). Does this energy depend only on the rest mass of the object; or one must take into account it's relativistic mass? In other words, if we imagine two identical bullets on the top...
  10. Bheshaj

    I Potential energy

    Can someone please explain me the concept of potential energy correctly and in detail.
  11. hilbert2

    A Delta potential in classical mechanics

    In quantum mechanics, there exist some systems where the potential energy of some particle is a Dirac delta function of position: ##V(x) = A\delta (x-x_0 )##, where ##A## is a constant with proper dimensions. Is there any classical mechanics application of this? It would seem that if I...
  12. navneet9431

    Does the Potential Energy increase during Chemical Bonding?

    Hi All, The Potential Energy for two chemically bonding atoms is defined by ,U=1/2(k*q1*q2)/r So it means that when the atoms approach each other then, their Potential Energy will increase. Where am I doing wrong? I will be thankful for help!
  13. Potential Energy of a Particle | Work done by Conservative Forces

    Potential Energy of a Particle | Work done by Conservative Forces

    What is a conservative force and how do you determine the work done by it. It is an interesting relation between the work done by such a force and the potential energy and kinetic energy of a particle.
  14. Benjamin Fogiel

    A rocket burns out at an altitude h above the Earth's surface

    1. Homework Statement A rocket burns out at an altitude h above the Earth's surface. Its speed v0 at burnout exceeds the escape speed vesc appropriate to the burnout altitude. Show that the speed v of the rocket very far from the Earth is given by v=(v02-v2esc)1/2 2. Homework Equations...
  15. C

    I Potential Energy for "stone + field" physical system

    Consider the classical scenario a stone falling in the Earth gravitational field. Classically we attach a Potential Energy to the stone and using the law of conservation of (mechanical) energy we are able to evaluate the dynamic of the falling stone. This model assume a stone in a "external"...
  16. J

    Moving down a ramp

    1. Homework Statement Please look at the problem attached as a screenshot. 2. Homework Equations Assuming frictionless, Ei = Ef, which means objects that are the same will end up in the same heights (so we can group A&C, B&D, and E&F). For A&C and E&F, mgh = KE_rot + KE_trans For B&D, it...
  17. J

    Do A and C have same or different KE at the end?

    1. Homework Statement Please look at the attached screenshot. 2. Homework Equations Assuming the ramp is frictionless, Ei = Ef and thus mgh = KE ( = 1/2mv^2, which isn't really necessary here) 3. The Attempt at a Solution I'm okay with all other examples except for A and C. From the...
  18. J

    Speed or turning point using energy

    1. Homework Statement Please look at the attached screenshot. This problem is really confusing for me and I can't seem to make much sense out of it. 2. Homework Equations Ei = Ef 3. The Attempt at a Solution As you can see, I did get (a). (The other checkmarks, I guessed — there were...
  19. Hawkingo

    B Calculating the P.E. of a system

    Let, we want to calculate the P.E(potential energy) of a system containing 3particles p1,p2,p3.the point of observation is P.so now we should add up the P.E at P due to p1,p2,p3 to get the net potential energy of the system,but why we take the P.E of particles due to each other into count...
  20. A

    How much work needs to be done on a piano to move it into the bed of a truck?

    1. Homework Statement Movers must push a piano onto a truck, the bed of which is a height 1.35 m above the ground. To do this they will use a frictionless ramp. If the piano has a mass of 1806.0 kg and the movers push it up the slope at a constant velocity, how much work do they need to do on...
  21. zachx

    I 2 Different Ways to Write Potential Energy of a Pendulum

    I have been doing pendulum problems lately, and I have found 2 different formulations for potential energy of a pendulum. U=mgl(1-cos(Θ)) and U=-mglcos(Θ) The first says U=0 when Θ=0 (at the bottom). The second has U=0 when Θ=π/2 (halfway to the top). Both give the same equation of motion...
  22. V

    Problem in understaning potential energy

    1. Homework Statement If we lift a block with constant velocity, by applying a force mg upwards, is the work done zero? 2. Homework Equations 3. The Attempt at a Solution The work done must be zero as the resultant force is zero, what I don't understand is how does the block get potential...
  23. A

    I Do electromagnetic waves have potential and kinetic energy

    Do electromagnetic waves have potential and kinetic energy like springs, strings, etc. If so how are they calculated, inter-related? What is the total energy? Are the energies fluctuating over time? I am a physics hobbyist so generally the first answers should come with the least mathematics...
  24. G

    B Energy Confusion (Conservation of Energy?)

    Anyone know if the following statement is true (and why)? "Getting to higher ground would increase his gravitational potential energy, decreasing the effects of non-conservative forces, which would allow him to move easier." CLARIFICATION: "move easier" refers to a lack of friction and not the...
  25. I

    I Relationship between force and potential energy

    I am aware that the negative derivative of potential energy is equal to force. Why is the max force found when the negative derivative of potential energy is equal to zero?
  26. Jackson Smith

    B Creation of PE - WHEN is it created?

    Generally, a change in altitude within a gravitational field is said to increase or decrease PE. I posit that the change in PE never occurs UNTIL there is a change in KE. Thus, in the case of an object with a constant velocity UP, there is no gain in PE until the instant that the thrust no...
  27. J

    Mechanical energy for planet in elliptical orbit around star

    1. Homework Statement A planet is in an elliptical orbit around a star. Which of the following best represents the mechanical energy E_planet of just the planet and the mechanical energy Es_tar-planet of the star-planet system as functions of time for one complete orbit? 2. Homework...
  28. A

    I Potential ##V## and potential energy ##E_{pot}##?

    Hi, I know that in an elecric field the potential energy ##E_{pot}## is equal to the potential ##V## times the charge ##E_{pot}=q V##. Here my problem: I know that the potential energy of a spring is ##E_{pot}= \frac{1}{2}kx^2##. In my theoretical physics book i read also that the potential is...
  29. A

    How close will body approach fixed point charge?

    1. Homework Statement Charged sphere with a mass of 15 mg and charge 2 nC moves with a speed of 15 cm/s towards a fixed point charge of 3 nC. How close will sphere approach charge? 2. Homework Equations K=(1/2)*mv2 U=k*(Q1Q2/r) 3. The Attempt at a Solution So I am not sure I approached...
  30. J

    Deriving gravitational potential energy -- mistake

    1. Homework Statement Hi I'm attempting to derive the gravitational potential energy of a point mass (##m##) that's moving from infinity to a point r' inside a gravitational field produced by a another mass ##M##. For simplicity I treated it as a one dimensional case. The problem I get is that...
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